A mononuclear hexacoordinate Cu(II) complex shows a field induced slow magnetic relaxation that is not facilitated by an energy barrier to spin reversal due to the zero-field splitting. Two relaxation channels were found: the magnetic field strongly supports the low-frequency relaxation path with a relaxation time as long as tau = 0.8 s at T = 1.9 K and B = 1.5 T. The mechanism of the relaxation at low temperature involves the dominant Raman process for this S = 1/2 spin system along with a temperature-independent term belonging to a quantum tunneling.